The saddle secured to a conventional bicycle is fixed at a certain angle, so a user on the saddle cannot change the angle if necessary and should ride with the angle of the saddle being fixed when riding on an inclination road, so the bicycle is inclined when riding on a high inclination road like a MTB, and the saddle remaining angle changes to an inclined state. In this state, the hips of the user become slid toward the rear side on the upper surface of the saddle, so the user cannot keep a proper posture. When the hips of the user slide to the front side on the upper surface of the saddle when the bike runs down on the inclined road, it is impossible to keep a proper posture, so the user cannot ride and drive the bike.